1 files changed, 65 insertions, 0 deletions
diff --git a/test/typeparam/combine.go b/test/typeparam/combine.go
new file mode 100644
index 0000000..361708f
--- /dev/null
+++ b/test/typeparam/combine.go
@@ -0,0 +1,65 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+type Gen[A any] func() (A, bool)
+
+func Combine[T1, T2, T any](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T] {
+	return func() (T, bool) {
+		var t T
+		t1, ok := g1()
+		if !ok {
+			return t, false
+		}
+		t2, ok := g2()
+		if !ok {
+			return t, false
+		}
+		return join(t1, t2), true
+	}
+}
+
+type Pair[A, B any] struct {
+	A A
+	B B
+}
+
+func _NewPair[A, B any](a A, b B) Pair[A, B] {
+	return Pair[A, B]{a, b}
+}
+
+func Combine2[A, B any](ga Gen[A], gb Gen[B]) Gen[Pair[A, B]] {
+	return Combine(ga, gb, _NewPair[A, B])
+}
+
+func main() {
+	var g1 Gen[int] = func() (int, bool) { return 3, true }
+	var g2 Gen[string] = func() (string, bool) { return "x", false }
+	var g3 Gen[string] = func() (string, bool) { return "y", true }
+
+	gc := Combine(g1, g2, _NewPair[int, string])
+	if got, ok := gc(); ok {
+		panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok))
+	}
+	gc2 := Combine2(g1, g2)
+	if got, ok := gc2(); ok {
+		panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok))
+	}
+
+	gc3 := Combine(g1, g3, _NewPair[int, string])
+	if got, ok := gc3(); !ok || got.A != 3 || got.B != "y" {
+		panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok))
+	}
+	gc4 := Combine2(g1, g3)
+	if got, ok := gc4(); !ok || got.A != 3 || got.B != "y" {
+		panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok))
+	}
+}